This invention relates to a device for testing brake fluid, and in particular to a device for testing the quality of brake fluid by measuring the conductivity of the brake fluid.
Water and corrosion products contaminate brake fluids, adversely affecting their performance and reducing their boiling points. Brake fluids are generally hygroscopic, i.e., they readily absorb water, and thus they rapidly deteriorate when exposed to water. This is a problem even for fresh brake fluid if it is not properly sealed. It has been experimentally determined that one percent moisture will lower the boiling point as much as 25% and three percent moisture will lower the boiling point 50%. This decrease in boiling point means that heat generated during the operation of the brakes can cause the water to boil out of the brake fluid, forming steam that impairs the operation of the brakes.
The deterioration of brake fluid is usually not apparent from the appearance of the brake fluid. For this reason at least some automobile manufacturers recommend that the brake fluid be frequently changed. Prior testing equipment for brake fluid was complicated, time consuming, and expensive. One prior device for testing brake fluid is disclosed in Klein et al., U.S. Pat. No. 4,566,805. This device operates by monitoring the temperature of a small heating element immersed in the fluid as the element is heated. The temperature of the element levels off briefly at the boiling point of the fluid, indicating the moisture content of the fluid.